1. Field of the Invention
The present invention relates to a microscope technology, and more particularly to a technology for modifying the magnification in coaxial epi-illumination.
2. Description of the Related Art
Generally, the optical performance of a microscope depends on the performance of an objective. However, without optimal illumination matched with the performance of an objective, a microscope cannot display its essential performance. Therefore, the illumination device of a microscope is provided with a field stop and an aperture stop, thereby realizing optimal illumination. Especially, if a field stop for controlling an illumination field is narrowed, contrast improves. Therefore, it is important to narrow the field stop to such degree that the vignetting of a field may not occur.
There is a technique for automating such control and automatically controlling illumination light. For example, Japanese Laid-open Patent Publication No. H5-016006 discloses a technique for simplifying the operation of a field stop, an aperture stop, an ND filter and the like.
The magnification modifying method of a microscope includes a turret method, a nose-piece method, a zoom method and the like. The turret method inserts a magnification modifying lens group in an observation optical path by an annular turret provided in the neighborhood of an observation optical path, on which the magnification modifying lens group is mounted. The nose-piece method inserts a magnification modifying lens group in an observation optical path by an objective nose-piece on which a plurality of objectives with different magnification. The zoom method moves a zoom lens group inserted in an observation optical path. In both the turret and nose-piece methods, magnification can be modified by preparing a lens group meeting a purpose in advance. In the zoom method, magnification can be continuously modified within the variable magnification range of a zoom lens group. However, since when magnification is modified, a field range is also modified accordingly, it is necessary to control a field stop according to magnification.
Japanese Laid-open Patent Publication No. H7-248450 discloses a configuration for automating the control of a field stop, an aperture stop accompanying magnification modification by using a display with touch panel and the like. Especially, since when modifying zoom magnification, an observation environment obtained by adjusting a field stop and the like before/after the modification of zoom magnification can be automatically maintained, troublesome operation can be reduced.
The above-described Japanese Laid-open Patent Publication No. H5-116006 defines an optimal stop diameter calculated on the basis of the magnification of an objective and a field diameter. However, this definition does not correspond to zoom magnification modification, intermediate magnification modification and the like. Although the defined equation is applicable to transparent illumination but not applicable to epi-illumination.
The configuration disclosed by Japanese Laid-open Patent Publication No. H7-248450 can maintain an observation environment obtained by adjusting a field stop and the like before/after the modification of zoom magnification. However, during modifying zoom magnification, a field stop blocks part of a field.